Topic: Beyer dynamic MV100 tests.

[Church-Audio]

I did some tests on the MV 100 here is what I found..

Chris

[Church-Audio]

What I am going to do with this preamp is take up the stupid three way switch and put in a pot for gain.. I am going to put in a 20db pad in the front end to reduce overload for really loud shows. And Last but not least change the feedback loop gain resistor in the unity gain amp on the output so it does not overload so easily. I have already replaced the opamps with That 1510 I have measured the preamp with the new opamps and all that they have done is flatten the frequency response so it's now dead flat from 20hz to 80khz.. I am going to change a few caps as well after I am done I will post the before and after tests.

Chris

[marc0789]

nice little box, but it's a joke that it overloads so easily. I ran 4022>mv100>modsbm1 for panic red rocks a couple of years ago. Even with the mapper set at 2 or so, I still was bouncing zeros, and clipped during a little wind gust.

[morst]

I am going to change a few caps as well after I am done I will post the before and after tests.

Did you ever do any more tests? I'm not sure I fully understand the graphics posted above, but I have had the mv100 for nearly 8 years and am considering upgrading the stock IC chip(s?) and possibly changing resistors to get lower gain options. I have never used the +60 dB setting and only used the +40 about 5 times.

By the way, here is the complete manual for it-
http://www.taperssection.com/reference/pdf/Manual_BeyerdynamicMV100.pdf

[Church-Audio]

I am going to change a few caps as well after I am done I will post the before and after tests.

Did you ever do any more tests? I'm not sure I fully understand the graphics posted above, but I have had the mv100 for nearly 8 years and am considering upgrading the stock IC chip(s?) and possibly changing resistors to get lower gain options. I have never used the +60 dB setting and only used the +40 about 5 times.

By the way, here is the complete manual for it-
http://www.taperssection.com/reference/pdf/Manual_BeyerdynamicMV100.pdf

I would change the resistors for sure lower everything by 10 db at least.. or consider putting in a gain pot a little more involved but it can be done. Changing the opamp did nothing really for the performance.. There are two main issues with this product 1- Power supply noise... 2- Bad gain stucture.

[morst]

I would change the resistors for sure lower everything by 10 db at least.. or consider putting in a gain pot a little more involved but it can be done. Changing the opamp did nothing really for the performance.. There are two main issues with this product 1- Power supply noise... 2- Bad gain structure.

Thanks kindly and +t for the response. I am thinking that gain settings of Unity (+0), +10, +20 would be good, or possibly +7, +14, +28 if there is some reason that +0 would be bad or noisy or something. Could anyone tell me exactly which resistors to change, and to what values? I can de-solder and re-solder if I have the recipe, but I'm not much for figuring out WHAT to install to get what you suggest. I actually like the switched gain since it affects both channels equally, thought I suppose a good quality ganged potentiometer would be sufficient, eh?

[Todd R]

I changed out the gain resistors years ago on my MV100 (now long since sold).  I think I set it up to have something like +12, +18, +28 instead of 20-40-60.

The gain resistors are weird.  One gain setting ( I think 20, but maybe 60) uses just one resistor, call it Resistor 1.  The next gain setting doesn't simply use Resistor 2, but instead uses the resistance from Resistor 1 in parallel with Resistor 2.  The final gain setting uses Resistor 1 in parallel with Resistor 2 in parallel with Resistor 3.  The whole thing makes choosing resistor values for particular gain ranges a pain.

Sorry, I don't remember where the resistors are anymore -- should be easy enough to trace out from the gain set switch.  In general, they're up close to the front of the unit, not that that helps much.

[morst]

The gain resistors are weird.  One gain setting ( I think 20, but maybe 60) uses just one resistor, call it Resistor 1.  The next gain setting doesn't simply use Resistor 2, but instead uses the resistance from Resistor 1 in parallel with Resistor 2.  The final gain setting uses Resistor 1 in parallel with Resistor 2 in parallel with Resistor 3.  The whole thing makes choosing resistor values for particular gain ranges a pain.

Sorry, I don't remember where the resistors are anymore -- should be easy enough to trace out from the gain set switch.  In general, they're up close to the front of the unit, not that that helps much.

I found this old thread where we were discussing this a while ago. I move slow when it comes to hardware mods!! 
http://taperssection.com/index.php/topic,22563.15.html

. . . it sounds like the 20db setting would be Resistor A || with Resistor B || with Resistor C.  Then 40 gain is Resistor B || with Resistor C, and 60db setting is just Resistor C.  Again, don't assume my memory on the specifics is right -- trace things out and double-check.  But they definitely use a design that uses the resistors in parallel with each other, rather than 3 different and separate resistors for the three different gain settings.

[DSatz]

Is there DC across the gain resistors? I have both the MV 100 and the Sonosax SX-M2, and the Sonosax's pots are quite noisy after very little use.

Not having checked the schematic, to me this is a hint that the pots have a DC voltage drop across them, which makes me glad to have a switch rather than a pot on the MV 100 even though its dB gradations are way too coarse.

--best regards

P.S.: BTW, in the 20 dB gain setting, I measured that the stock MV 100 clips at about -5 dBu in. The clip LED is set quite conservatively, i.e. it lights up 6 or 7 dB before there is any actual clipping, and this may have convinced some people that the preamp is a little easier to overload than it really is. It can handle the full output of a Schoeps mike at 124+ dB SPL, which would be louder than anything I've recorded in the past decade or two (including close-miked, professional opera singers).

[Church-Audio]

Is there DC across the gain resistors? I have both the MV 100 and the Sonosax SX-M2, and the Sonosax's pots are quite noisy after very little use.

Not having checked the schematic, to me this is a hint that the pots have a DC voltage drop across them, which makes me glad to have a switch rather than a pot on the MV 100 even though its dB gradations are way too coarse.

--best regards

P.S.: BTW, in the 20 dB gain setting, I measured that the stock MV 100 clips at about -5 dBu in. The clip LED is set quite conservatively, i.e. it lights up 6 or 7 dB before there is any actual clipping, and this may have convinced some people that the preamp is a little easier to overload than it really is. It can handle the full output of a Schoeps mike at 124+ dB SPL, which would be louder than anything I've recorded in the past decade or two (including close-miked, professional opera singers).

Well I did not measure the clip light I measured the THD THD+N and it overloads pretty easily compared to other preamps I have tested. As far as DC on the pots that can be fixed with some caps.

[morst]

According to the manual, the MV100 peak lights come on at -6dB below clip, but that is referenced vs the DC power supply voltage. Also, it says the "low battery" indicator lights go red below 14v.